ROGERS, Circuit Judge:
In these appeals from their convictions by a jury of conspiracy to distribute cocaine base, 21 U.S.C. § 846, distribution of cocaine base, id. § 841, and distribution of cocaine base within 1,000 feet of a school, in violation of id. § 860(a), appellants Lorenzo J. Baylor and Walter Jamal Smith raise separate and joint challenges. Smith contends that the district court abused its discretion in curtailing cross-examination of a key government witness on the subject of a prior conviction. Smith also contests the sufficiency of the evidence to sustain his conviction for drug distribution within 1,000 feet of a school. Both appellants challenge the sufficiency of the evidence to support their convictions for conspiracy. Baylor further contends that the district court clearly erred by increasing his base offense level to reflect his managerial role in the drug transactions, by failing to consider a downward departure based on a Sentencing Commission Report on cocaine sentencing policy, and by including as relevant conduct for purposes of calculating his base offense level drug amounts involved in counts of which he was acquitted. We affirm the judgments of conviction but, in view of the merger of the distribution counts with the "schoolyard statute" drug possession counts, we remand the case to the district court.
I.
The government's evidence showed that in 1994 appellants Baylor and Smith, and indicted co-conspirator Douglas Coates, worked together to complete a series of transactions involving the distribution of cocaine base. Viewed in the light most favorable to the government, Glasser v. United States, 315 U.S. 60, 80, 62 S.Ct. 457, 469-70, 86 L.Ed. 680 (1942), the evidence established that Baylor supplied the drugs to Coates, who then provided them to Smith for retail sale. On April 4, 1994, Coates introduced Smith to an undercover police officer at an apartment house located at 704 3rd Street, N.W., which was 534 feet from the Georgetown Law Center. Smith, the officer, and another man went to a small apartment located in the basement level of the building, where Smith produced a gym bag containing a large quantity of white rock substance. Smith then sold 10.21 grams of cocaine base to the officer for $500.
Following two other sales in April 1994 by Coates to the undercover officer, and after reporting that his supplier had just ordered a price increase to $1,200 for an ounce of crack, Coates introduced the officer to "his man" Baylor on May 19, 1994. After the officer gave Coates the money, Coates and Baylor entered a barbershop located in the one thousand block of U Street, N.W. When Coates returned he handed the officer a bag containing 21.431 grams of cocaine base. Coates stated that the quality of the cocaine was identical to that purchased by the officer on the three prior occasions. The May 19th sale occurred within 302 feet of Garnett Patterson Junior High School.
Prior to trial, Coates pled guilty to the distribution of 50 grams or more of cocaine base and agreed to testify for the government. Coates described his relationship with Baylor and Smith as having commenced in March 1993 when Baylor began to "front" between half an ounce and an eighth of a kilogram of cocaine base to Coates two or three times a week. Coates either sold the drugs himself or supplied other sellers, and paid Baylor only once the drugs were sold. Baylor determined where the two men would meet, the price of the cocaine sold, and whether Coates would be compensated in cash or cocaine. It was during this same period that Smith first approached Coates to ask whether he could procure drugs for him. In March and April 1993, Coates twice supplied Smith with one to two ounces of cocaine base that had been provided to him by Baylor. Monies paid by Smith to Coates were remitted to Baylor who, in turn, paid Coates a commission in the form of either money or cocaine. Smith informed Coates that he was selling the drugs at a homeless shelter located at 2nd and D Streets, N.W., and later at 704 3rd Street, N.W., and that he had two or three other persons working for him. Although the two lost contact during the summer of 1993, Smith approached Coates in October of that year to ask if Coates could still "work the deals for him." From November 1993 through March 1994, Coates sold Smith an eighth of a kilogram of cocaine base on six separate occasions. Each delivery was made with cocaine that had been provided to Coates by Baylor.
At trial, the government presented expert evidence concerning the typical features of drug conspiracies in the District of Columbia. According to the expert, drug distribution chains are frequently structured so that wholesalers and retailers have no direct contact with one another and instead work entirely through intermediaries.
In their defense, both appellants sought to impeach Coates' testimony. In addition to presenting other witnesses, Baylor testified that he had never had an agreement with Coates to sell drugs, and Smith denied that he ever bought cocaine from Coates. Following the government's rebuttal, the jury found Smith guilty of the April 4, 1994, distribution count, Baylor guilty of the May 19, 1994, distribution count, and both defendants guilty of conspiracy. Baylor was acquitted on counts relating to the distributions on April 4,13, and 20,1994.
II.
Appellant Smith contends that the district court erred in restricting his cross-examination of Coates on the subject of Coates' prior conviction under the Bail Reform Act. On direct examination, Coates admitted his prior convictions for drug distribution, conspiracy to distribute cocaine, and violation of the Bail Reform Act. On cross-examination, Coates stated that the Bail Reform Act conviction had resulted not from his failure to perform under the conditions of his bail, but because he missed a court date. When asked by defense counsel why he had missed it, Coates explained that he had been incarcerated at the time. He then admitted to having been sentenced for the violation. At this point, the prosecutor objected that the inquiry went well beyond proper impeachment. Smith's counsel argued that he was entitled to inquire whether Coates had violated the conditions of his release in order to test his trustworthiness. In sustaining the objection, the district court ruled that "[Y]ou cannot go into the details of the conviction."
Under Federal Rule of Evidence 609(a), when evidence of a prior conviction is admitted for purposes of impeachment, cross-examination is usually limited to the essential facts rather than the surrounding details of the conviction. United States v. Castro, 788 F.2d 1240, 1246 (7th Cir.1986). Courts have recognized, however, that under certain circumstances details concerning a conviction may be elicited, and the district court's determination as to the nature and extent of the inquiry is reviewed for abuse of discretion. See e.g., United States v. Swanson, 9 F.3d 1354, 1357 (8th Cir.1993). On appeal the government maintains that once the na ture and date of Coates' Bail Reform Act conviction were established, Smith had no right to probe the underlying facts. Citing United States v. Butler, 924 F.2d 1124, 1130 (D.C.Cir.), cert. denied, 502 U.S. 871, 112 S.Ct. 205, 116 L.Ed.2d 164 (1991), however, the government acknowledges that a witness may "open the door" to more extensive cross-examination by attempting to minimize the conduct for which he was convicted.
Without knowing the facts underlying Coates' Bail Reform Act conviction, Coates' answers on cross-examination might well have been interpreted by a reasonable juror as an attempt to explain away the conviction. Certainly, Coates' testimony implied that he thought his incarceration was a defense to the Bail Reform Act charge. Consequently, Smith contends that the district court abused its discretion by cutting off cross-examination of a key government witness without allowing the defense an opportunity to ensure that the jury would understand the nature of Coates' conviction and could evaluate whether his explanation was credible.
Although we agree with the government that Coates' testimony sufficed to explain to the jury the basic nature of a Bail Reform Act violation, see D.C.Code § 23-1327, Coates' claim that he was incarcerated at the time could reasonably have been interpreted by the jury to suggest that Coates was unfairly convicted. Given the centrality of Coates' testimony and the efforts made by the defense to cast doubt on his credibility, the district court might well have afforded counsel some additional leeway in order to clarify the circumstances of the conviction. See United States v. Wolf, 561 F.2d 1376, 1381 (10th Cir.1977). The usual reason for' caution with respect to the scope of cross-examination concerning a witness' prior conviction, namely, the need to protect from undue prejudice a defendant who takes the stand, is not at issue where, as here, the witness is not on trial. See United States v. Mitchell, 427 F.2d 644, 647 (3rd Cir.1970); Fed.R.Evid. 609(a) (referencing Federal Rule of Evidence 403). Still, absent some indication that additional cross-examination would have a measurable and independent impeachment value, the district court could reasonably want to avoid a mini-trial on Coates' Bail Reform Act conviction. On balance, the district court may simply have concluded that the jury had heard' enough and appellants had nothing more to gain.
In any event, because the jury was aware of Coates' other convictions and learned that his plea agreement created an incentive for him to give testimony that would be viewed favorably by the government when he was later sentenced, any error in barring further impeachment was harmless. See Kotteakos v. United States, 328 U.S. 750, 764-65, 66 S.Ct. 1239, 1247-48, 90 L.Ed. 1557 (1946). Any incremental inquiry regarding the Bail Reform Act conviction would have had little impeachment value, particularly since the undercover officer's testimony was sufficient to support the conviction for the April 4, 1994, sale, and his testimony about the May 19, 1994, sale corroborated Coates' general account of the workings of the conspiracy.
III.
More problematic is appellant Smith's contention that the government failed to offer sufficient evidence to show that on April 4, 1994, Smith sold drugs within 1,000 feet of a school. Specifically, he contends that the government failed to prove that the basement apartment at 704 3rd Street, N.W., was less than 1,000 feet from the Georgetown University Law Center. While the government introduced evidence that the distance between the Law Center and the "building line" of the apartment building at 704 3rd Street was 534 feet, it did not present a measurement reflecting the location of the actual apartment in which the April 4th drug sale occurred.
Under the "schoolyard statute," 21 U.S.C. § 860(a), which provides for enhancements for drug offenses, the government must prove that the possession of drugs occurred within 1,000 feet of a school. In United States v. Johnson, 46 F.3d 1166 (D.C.Cir.1995), the court stated that, irrespective of actual pedestrian travel routes, a straight line measurement can suffice to meet the requirements of the statute. Id. at 1169-70. The court in Johnson reversed the conviction, however, because the pedestrian route measurement of 994 feet only went up to the steps of the house and did not include the distance to the actual point within where the drug possession had occurred. Id. at 1170. The court observed that the government could not meet its burden of proof simply by asserting that a straight line distance would necessarily have been considerably shorter than the pedestrian route that formed the basis of the measurement offered in evidence. Id. In contrast to United States v. Watson, 887 F.2d 980 (9th Cir.1989) where evidence included a map that enabled the jury to approximate the distance omitted from the government's measurement, id. at 981, the court noted that the jury in Johnson had no such evidence upon which it could have based a similar conclusion. Johnson, 46 F.3d at 1170.
Consequently, in the instant case, the question is whether a measurement of 534 feet from the Law Center to the apartment building combined with the other evidence concerning the location of the relevant buildings and streets suffices to meet the government's burden of proof. A government evidence technician explained that, to arrive at the 534-foot measurement between the Law Center and the apartment building, he measured from the "building line" at 704 3rd Street to the wall of the freeway that separates 3rd Street from the Law Center, and then went north to Massachusetts Avenue, which crosses the freeway, and then measured across 2nd Street to the Law Center library. No direct evidence was introduced concerning the location of the basement apartment where the drug transaction took place, or the distance between the apartment and the exterior wall of the apartment building where the measurement was taken. The government did introduce into evidence a schematic map designed to show the spatial relationship between the apartment building and the Law Center, as well as three photographs that depicted the front of 704 3rd Street, N.W., the view of the apartment building from the Law Center, and the view of the Law Center from the apartment building.
The government maintains that the evidence was sufficient to enable a reasonable jury to conclude that the apartment building does not occupy the entire block bounded by 3rd, G, 4th, and H Streets, N.W. Thus, it contends, it would have been impossible for the basement apartment to have been as distant from the Law Center as the far northwest corner of the block depicted in the schematic map. Further, even if the building did occupy the entire block and the apartment were at the opposite corner of the block from the point where the measurement was taken, the map demonstrates that the length of the G Street block would not have pushed the total measurement over 1,000 feet. The government points out that because the distance between the Law Center and the eastern wall of the apartment building — encompassing the width of 3rd Street, the block between 3rd Street and the freeway, the freeway itself, the block between the freeway and 2nd Street, and 2nd Street — equals only 534 feet, it would be unreasonable to conclude that the width of the apartment building itself and the distance down to the basement could approach 466 feet.
Although the map was not introduced by the government for purposes of illustrating the 1,000 foot measurement and was never established as having been drawn to scale, it was in evidence before the jury as accurately depicting the location of the apartment building at 704 3rd Street and the surrounding area. The diagram showed that the building was located at the corner of 3rd and G streets. We conclude that when considered in combination, the 534-foot measurement, map, and photographs were sufficient to permit a reasonable juror to conclude that the distance from the "building line" to the basement apartment did not exceed .466 feet. Spatial relationships are hardly intuitive, and photographs can distort distances. Nevertheless, given the evidence regarding the vast area represented by the 534-foot measurement, the jury could have concluded that the physical configuration that would have been required for the unmeasured area be tween the "building line" and the basement apartment to be 466 feet or more was fundamentally inconsistent with the photographs of the apartment building and the adjacent streets as well as the schematic map. Smith's speculation that the basement apartment might have been several floors below ground is contradicted by the undercover officer's testimony that the apartment was on "the lower level" (emphasis added). In contrast to both Johnson and United States v. Applewhite, 72 F.3d 140 (D.C.Cir.1995), cert. denied, — U.S. -, 116 S.Ct. 1864, 134 L.Ed.2d 962 (1996), on which Smith relies, where the government faced the difficulty of showing that its evidence precluded a finding that an unmeasured leg could have been more than 80 feet long, here the government had far more spatial leeway, and needed only to show, through the photographs and map, that the missing distance was 466 feet or less. Obviously, the government should not undermine its own case by offering incomplete measurements. Under the circumstances, however, with substantial room to spare before reaching the 1,000 foot limit, the government's measurement, when combined with the map and the photographs of the buildings and the freeway, was sufficient to show that the April 4 sale occurred within 1,000 feet of a school.
IV.
Neither appellant's contention that there was insufficient evidence to support his conviction for conspiracy is persuasive. See Glasser, 315 U.S. at 80, 62 S.Ct. at 469-70. The evidence showed an agreement between two or more persons to distribute cocaine and that appellants were knowing participants in the agreement. See United States v. Thorne, 997 F.2d 1504, 1512 (D.C.Cir.), cert. denied, 510 U.S. 999, 114 S.Ct. 568, 126 L.Ed.2d 467 (1993); United States v. Lam Kwong-Wah, 924 F.2d 298, 303 (D.C.Cir.1991), cert. denied, 506 U.S. 901, 113 S.Ct. 287, 121 L.Ed.2d 213 (1992). In the face of overwhelming evidence of Baylor's complicity in a series of drug transactions, his acquittal on charges of aiding and abetting transactions that took place in April 1993 is irrelevant. See United States v. Morris, 836 F.2d 1371, 1373 (D.C.Cir.1988). Notwithstanding Baylor's attempts to discredit Coates' testimony, he did not introduce evidence that contradicted Coates' basic description of the dealings between himself and Baylor. As the government points out in its brief, that the jury might have been unwilling to rely exclusively on Coates' testimony to convict Baylor of transactions of which he was not specifically aware does not mean that the jury rejected Coates' testimony entirely.
Although appellant Smith argues that the evidence showed nothing more than a buyer-seller relationship between himself and Coates, there was testimony that Coates introduced the undercover officer to Smith and that Smith advised the officer that he could be contacted through Coates. The evidence also showed that Smith originally approached Coates to determine if he would procure wholesale quantities of drugs for him, thus recognizing that Coates would act as a middleman between Smith and a supplier who would turn out to be Baylor. That Smith never met Baylor is irrelevant. United States v. Jenkins, 928 F.2d 1175, 1178 (D.C.Cir.1991); United States v. Tarantino, 846 F.2d 1384, 1392 (D.C.Cir.), cert. denied, 488 U.S. 867, 109 S.Ct. 174, 102 L.Ed.2d 143 (1988); see also United States v. Childress, 58 F.3d 693, 709-10 (D.C.Cir.1995), cert. denied, — U.S. -, 116 S.Ct. 825, 133 L.Ed.2d 768 (1996). The size of the orders that Coates was able to fill provided an additional basis upon which a jury could conclude that Smith knew he had tapped into an established drug operation. From this evidence a reasonable jury could find that Smith and Coates were working together in an ongoing, cooperative purchaser-middleman relationship where they were dependent upon one another for drugs and profits respectively. See United States v. Sobamowo, 892 F.2d 90, 94 (D.C.Cir.1989), cert. denied, 498 U.S. 825, 111 S.Ct. 78, 112 L.Ed.2d 51 (1990); United States v. Medina, 944 F.2d 60, 65-66 (2d Cir.1991), cert. denied, 503 U.S. 949, 112 S.Ct. 1508, 117 L.Ed.2d 646 (1992).
V.
Finally, Baylor's sentencing challenges fail. His challenge to the district court's increase of his base level by two points to reflect his managerial role under the United States Sentencing Guidelines ("U.S.S.G.") § 3Bl.l(e) (1994) is meritless. The district court had sufficient evidence on which to conclude that Baylor exercised control over and organized the activities of at least one other person involved in distributing the drugs. See United States v. Hazelett, 80 F.3d 280, 284 (8th Cir.1996). Relying upon the evidence concerning Baylor's role in the May 19, 1994, transaction and Coates' testimony about Baylor's decision-making authority, we find no clear error. See United States v. Sutera, 933 F.2d 641, 649 (8th Cir.1991).
Nor has Baylor shown that a remand is warranted to enable the district court to consider a downward departure under U.S.S.G. § 5K2.0. His reliance on the Sentencing Commission's Special Report of February 1995 criticizing the present 100:1 ratio for weighing cocaine base and cocaine powder is unavailing in light of United States v. Anderson, 82 F.3d 436 (D.C.Cir.1996). Although, for reasons set forth in the opinion of Judge Wald, concurring specially, infra, Baylor's challenge to the district court's treatment as relevant conduct of drug amounts involved in the counts for which he was acquitted is not without persuasive force, United States v. Boney, 977 F.2d 624, 635-36 (D.C.Cir.1992), is controlling in this circuit.
YI.
Accordingly, we affirm the judgments of conviction. All parties agree, however, that the convictions for the April 4 and May 19 distribution counts, 21 U.S.C. § 841, merge with the convictions under the "schoolyard statute," 21 U.S.C. § 860(a). See Blockburger v. United States, 284 U.S. 299, 304, 52 S.Ct. 180, 182, 76 L.Ed. 306 (1932); United States v. Whren, 53 F.3d 371, 376 (D.C.Cir.1995), aff'd, — U.S.-, 116 S.Ct. 1769, 135 L.Ed.2d 89 (1996). At the time appellants were sentenced, courts in this circuit followed the practice of imposing sentences on all counts of which a defendant was convicted, leaving vacation of any lesser count until completion of the appeal. See e.g., United States v. Dale, 991 F.2d 819, 859 (D.C.Cir.), cert. denied, 510 U.S. 1030, 114 S.Ct. 650, 126 L.Ed.2d 607 (1993). See also United States v. Aiello, 771 F.2d 621, 634 (2d Cir.1985); United States v. Fernandez, 916 F.2d 125, 128-29 (3d Cir.1990), cert. denied, 500 U.S. 948, 111 S.Ct. 2249, 114 L.Ed.2d 490 (1991). Most recently, in Rutledge v. United States, — U.S. -, 116 S.Ct. 1241, 134 L.Ed.2d 419 (1996), the Supreme Court clarified Ball v. United States, 470 U.S. 856, 105 S.Ct. 1668, 84 L.Ed.2d 740 (1985), in which the Court had stated that, when a defendant is found guilty of both lesser and greater offenses, the district court should enter judgment on only one of the counts. Id. at 865, 105 S.Ct. at 1673-74. The Rutledge Court rejected the use of multiple convictions to provide a "back up" conviction in order to ensure that a defendant who successfully challenges a greater offense does not escape punishment. — U.S. at-, 116 S.Ct. at 1249. "[W]hen a conviction for a greater offense is reversed on grounds that affect only the greater offense," the Court explained, the appellate court "may direct the entry of judgment for a lesser included offense." Id. at-, 116 S.Ct. at 1250. Thus, the Court indicated that the district court should instruct the jury "not to return a verdict on a lesser included offense once it has found the defendant guilty of the greater offense." Id. at-n. 16, 116 S.Ct. at 1250 n. 16.
While the government seeks remand only for vacation of the judgments on the § 841 counts, appellants contend that resentencing is warranted in light of the sentencing range available to the district court under the Sentencing Guidelines. Because the district court made a sufficient record of its intentions at trial, indicating that its awareness of the merger issue and its concern about the government's duplicative charging practices would cause it to impose only concurrent sentences if appellants were convicted on both the greater and lesser counts, a remand for resentencing would appear unnecessary. See United States v. Lewis, 482 F.2d 632, 647 (D.C.Cir.1973); United States v. Wimbush, 475 F.2d 347, 348 (D.C.Cir.1973); see also United States v. McKnight, 17 F.3d 1139, 1147 (8th Cir.1994) (Magill and Hansen, JJ., concurring), cert. denied, — U.S.-, 115 S.Ct. 275, 130 L.Ed.2d 192 (1994). Given the absence of clear circuit precedent on point since the enactment of the Sentencing Guidelines, cf. United States v. Fennell, 77 F.3d 510, 510-11 (D.C.Cir.1996) (per curiam), we remand the cases so that the district court can vacate each appellants' judgment of conviction for the distribution counts, without prejudice to appellants' right to seek resentencing in light of vacation of one of their convictions.
. Appellants have waived any challenge to the constitutionality of the "schoolyard statute," 21 U.S.C. § 860(a), because they failed to raise this issue in the district court. United States v. Baucum, 66 F.3d 362 (D.C.Cir.1995), cert. denied, — U.S.-, 117 S.Ct. 204, 136 L.Ed.2d 139 (1996).
. The government does not contend that Smith failed to preserve this issue by raising it in the district court, and we express no opinion on the nature of a sufficient objection.